1. Field of Invention
This invention relates to a projector for projecting and displaying an image.
2. Description of Related Art
In a projector, light emitted from an illuminating system is modulated by liquid crystal panels or the like according to image information (image signals), and the modulated light is projected onto a screen, thereby achieving image display.
FIG. 9 is an explanatory view showing a principal part of a conventional projector. The projector may consist of three liquid crystal light valves 900R, 900G, and 900B, a cross-dichroic prism 920, and a projection system 940. Light of the three colors red (R), green (G), and blue (B) emitted from an illuminating system (not shown) passes through the liquid crystal light valves 900R, 900G, and 900B, whereby the light is modulated according to image information. The modulated light (modulated light beams) is synthesized by the cross-dichroic prism 920, and the synthesized light is projected by the projection system 940. This allows a color image to be displayed on a screen SC.
The first liquid crystal light valve 900R may include a liquid crystal panel 901R, and two polarizers 902Ri and 902Ro bonded on the side of the light incident surface and on the side of the light emitting surface of the liquid crystal panel 901R, respectively. The first polarizer 902Ri on the side of the light incident surface transmits light polarized in the same direction as the polarization axis in the light incident thereon. In FIG. 9, since it is assumed that the light incident on the first polarizer 902Ri is polarized in substantially the same direction as the polarization axis of the first polarizer 902Ri, almost all of the incident light passes unchanged through the first polarizer 902Ri. The light transmitted by the first polarizer 902Ri is converted into light polarized in a predetermined direction by the liquid crystal panel 901R and the second polarizer 902Ro, and is emitted. This also applies to the second and the third liquid crystal light valves 900G and 900B.
Incidentally, when light emitted from the illuminating system is applied to the liquid crystal light valves, the polarizers of the liquid crystal light valves usually produce heat. In this case, the temperature of the polarizers is sometimes increased to a high temperature of about 80xc2x0 C. This is because the light that is not transmitted by the polarizers is absorbed by the polarizers. In FIG. 9, since it is assumed that light polarized in substantially the same direction as the polarization axes of the polarizers on the side of the light incident surfaces enters the liquid crystal light valves 900R, 900G, and 900B, the polarizers 902Ri, 902Gi, and 902Bi on the side of the light incident surfaces produce relatively little heat. On the other hand, since the polarizers 902Ro, 902Go, and 902Bo on the side of the light emitting surfaces transmit only the light polarized in a predetermined direction in the light modulated by the liquid crystal panels, and absorb light polarized in other directions, they produce a relatively large amount of heat. If a black image is displayed on the screen SC, the polarizers 902Ro, 902Go, and 902Bo on the side of the light emitting surfaces absorb almost all of the incident light. Therefore, they produce a considerable amount of heat.
When the polarizers produce heat in this way, thermal stress is generated inside the polarizers because the polarizers are bonded to the liquid crystal panels. When the polarizers are bonded to lenses or prisms, thermal stress is similarly generated inside the polarizers. FIG. 10 is a plan view of the second polarizer 902Ro bonded on the side of the light emitting surface of the first liquid crystal panels 901R as viewed from the -x direction. The thermal stress inside the polarizer is exerted in the directions shown by the arrows in FIG. 10, and a strain due to the thermal stress is generated in the polarizer. The strain also depends on an intensity distribution of light incident on the polarizer, but usually gets larger, particularly in areas encircled by broken lines shown in FIG. 10, that is, at four comers of the nearly rectangular polarizer 902Ro. When the polarizer strains in this way, the polarizer cannot exhibit desired characteristics. That is, the polarizer 902Ro may transmit light that should be shielded, or shield light that should be transmitted. In this case, light emitted from a strained portion of the polarizer is elliptically polarized, and the intensity of light may increase or decrease as compared with a normal case in which a linear polarized light is emitted. It is believed that such a phenomenon occurs because of strain generated in the molecular structure of the polarizer, and that such a phenomenon depends on the alignment of liquid crystal molecules that determines the polarization direction of light incident on the polarizer 902Ro. When the thermal stress is generated in the polarizer 902Ro in this way, the modulated light beams to be emitted have inconsistencies in brightness. Therefore, when the modulated light beams are synthesized to display a color image on the screen SC, there is a problem in that inconsistencies in color arise in the image. Similarly, when a monochrome image is displayed on the screen SC, there is a problem in that inconsistencies in brightness arise.
This invention is achieved to at least solve the above-described problems in the conventional art. One exemplary object thereof is to provide a technique that is able to at least reduce inconsistencies in an image to be displayed in a projector.
A device in accordance with an exemplary embodiment of the present invention is a projector which may include an illuminating system for emitting illumination light; an electro-optical device for modulating light from the illuminating system according to image information; and a projection system for projecting a modulated light beam obtained by the electro-optical device. In addition, the electro-optical device of this exemplary embodiment preferably includes a polarizer on at least one of the sides of a light incident surface and a light emitting surface, and the polarizer is preferably bonded on a sapphire glass plate.
Since the sapphire glass has high heat conductivity, the temperature rise due to heat produced by the polarizer can be controlled, and the flexion of the polarizer due to thermal stress can be reduced. Therefore, inconsistencies in light emitted from the polarizer can be reduced, and consequently, it is possible to reduce inconsistencies in an image to be displayed.
The sapphire glass plate of this exemplary embodiment may preferably be formed of single-crystal sapphire. Since the single-crystal sapphire glass has particularly high heat conductivity, the above-described advantage is remarkably offered.
In addition, the sapphire glass plate of this exemplary embodiment may preferably be held by a plate member holding portion made of metal. This allows heat produced in the polarizer to be easily radiated to the outside via the sapphire glass plate and the plate member holding portion, and it is therefore possible to reduce the temperature rise and flexion of the polarizer.
Furthermore, the sapphire glass plate and the plate member holding portion are preferably bonded by an adhesive agent. This brings the sapphire glass plate and the plate member holding portion into face-to-face contact, and heat can therefore be transferred from the sapphire glass plate to the plate member holding portion more efficiently.
The sapphire glass plate may preferably be held in a state such that a space in which air can flow exists in at least a part of both surfaces of the sapphire glass plate. This can radiate heat from both surfaces of the sapphire glass plate by the heat transfer due to airflow, and it is possible to reduce the temperature rise and the flexion of the polarizer more efficiently.
A device in accordance with another exemplary embodiment of the present invention is a projector for projecting and displaying a color image, which may include an illuminating system for emitting illumination light; a color light separation system for separating the illumination light emitted from the illuminating system into first colored light, second colored light and third colored light having three color components, respectively; first electro-optical device, second electro-optical device and third electro-optical device for respectively modulating the first colored light, the second colored light and the third colored light separated by the color light separation system according to image information to respectively produce first modulated light beam, second modulated light beam and third modulated light beam; a color synthesizing section for synthesizing the first modulated light beam, the second modulated light beam and the third modulated light beam; and a projection system for projecting synthesized light emitted from the color synthesizing section. In addition, in this exemplary embodiment, each of the first to third electro-optical devices preferably includes a polarizer formed on at least one of the sides of a light incident surface and a light emitting surface, and the polarizer is bonded on a flexible light-transmissive plate member that flexes according to the change in the shape of the polarizer.
In the projector of this exemplary embodiment, in a manner similar to the above-described projector, inconsistencies in light emitted from the polarizer can be reduced, and it is possible to reduce inconsistencies in an image to be displayed.